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By Bahram Rezai

Fine particles float poorly and less-selectively under normal flotation conditions. One of the promising methods for fine minerals is the utilization of the principle of Flocculation. Hydrophobic flocculation flotation (or floc flotation) was tested on a magnetite concentrate that was finely ground to be micron particles, for producing a concentrate with sulphur grade less than 0.1%. After that, slurry dispersing with water glass as dispersant, pyrite fines were subjected to hydrophobic flocculation induced by xanthate and a small amount of kerosene then the slurry was transferred to a flotation cell for recovering the hydrophobic flocs. The experiments carried out indicated that through one-step rougher and two-step cleaner flotation, sulphur grade was reduced from 1% to 0.1%. It has been found that the separation efficiency of the floc flotation process closely correlates with the main parameters of hydrophobic flocculation such as xanthate addition, conditioning time and kerosene addition.

Jan 1, 2006

By Alex Mezei

Experimental rheology data are needed to produce design criteria for mass and energy transfer processes. Large throughput plants operate under continuous flow mode. The capital cost is determined by the accuracy of the rheology data used for design. The operating cost is dictated by the energy required to sustain the flowing conditions of various process slurries. Typically, rheology investigations are carried out during the final stages of metallurgical testwork, which is too late to set the design criteria for the pilot plant. This leads to increased testwork cost, and sometimes lowers confidence in the quality of the data produced. In addition, the engineering and feasibility studies are often delayed because of the lack of pertinent rheology data. One of the objectives of this paper is to emphasize the importance of timely planning and execution of the rheology study, which is shown to be a critical component of the overall testwork program. Various applications are discussed, including elaboration of process and equipment design criteria. In this paper, the emphasis is placed on gold and nickel laterite hydrometallurgy applications.

Jan 1, 2003

By Steven Wright

BHP Billiton?s Olympic Dam copper flash smelter employs the direct to blister process for smelting high grade copper concentrates. SO2 evolution during tapping gives rise to safety concerns. A thermodynamic model for the blister copper (Cu-Fe-S-O) was used to predict the volumes of SO2 evolved. The Multiple Phase Equilibria Model (MPE) was used to evaluate the slag chemistry inside the furnace. The blister copper model was used to explore the relationship between %S and %O in the copper and the amount of SO2 evolved on cooling. The volume of SO2 evolved was sensitive to the O content with reduction to levels below 0.2 ? 0.15% likely to suppress SO2evolution on cooling. Concentrations of S and O in copper samples from trials generally lay above the equilibrium line calculated for an average temperature of 1275C and a partial pressure of SO2 of 1 atm. Consequently there is a thermodynamic driving force for SO2evolution when cooling to this temperature during tapping. A number of potential process options to suppress SO2 evolution on tapping were investigated thermodynamically. Some of the options require treatment of the blister in a forehearth or separate furnace, while others impact on current practises in the flash furnace with slag present. The opportunities that these options present are discussed.

Jan 1, 2006

By Kenji Monden

"In order to obtain basic data for the development of highly thermally conductive composite materials, the thermal conductivity of a resin composite material with an Aluminum Nitride filler was assessed. Several different measurement techniques such as the xenon flash and the temperature wave thermometric analysis method were employed to gather data on these composites. An excellent match between theoretical and experimental data was achieved by employing a predictive expression that takes into account the effect of percolation on thermal conductivity.IntroductionA thermal solution composite is made by incorporating dense inorganic fillers with high thermal conductivity into a resin. Because the composite materials have high thermal conductivities, they have been used in electrical products that generate excessive thermal energy during operation, such as inverters, amplifiers and motor drivers. They function as electrically insulating and thermally conducting parts of the electric modules. As the uses of thermal solutions are expanded, composites of higher thermal conductivities will be required. The aim of this work was to investigate, evaluate, and try to predict the influence of key parameters on thermal conductivity and diffusivity. This was achieved by analyzing the effect of both volume fraction and shape of Aluminum Nitride ceramic fillers and measuring the thermal conductivity. In addition, the influence of percolation on thermal conductivity is considered. The thermal conductivity of the composites is discussed by employing a predictive equation using literature data of thermal conductivities for both the filler and resin. As well as thermal conductivity measurements the effect of volume fraction of the filler was also explored.ExperimentalSpecimen PreparationThe composite samples were prepared from silicone resin and Aluminum Nitride (AlN) fillers. The AlN fillers with an average particle size of 20 µm are shown in Figure 1. The mean diameters of the AlN particles used are given in Table I. For comparison the AlN fillers with an average particle size of 5 µm are shown in Figure 2. A planetary centrifugal mixer was used for simultaneously dispersing the components uniformly and de-aerating the mixture. After mixing, these materials were placed in a silicone rubber case and cured at 150 °C for 1 hour."

Jan 1, 2013

By Linping Yu

A simplified ED process was developed for organic acids recovery from cyclohexanone waste in this paper. In this regard, the one-stage ED was investigated directly without pretreatment, such as ion-exchange or nanofiltration to removal of foulants. The current efficiency and the energy consumption in the ED process for the recovery of carboxylic acids from cyclohexanone waste is theoretically analyzed and experimentally tested. The concentration of recovered carboxylic acid is related to many parameters and still needs more work to be determined.

Jan 1, 2009

By M. C. Nielson

The paper describes the design and operation of pulsed columns as replacements for conventional mixer/settlers. The advantages, which the columns offer, include a reduction in real estate for the plant, elimination of diluent evaporation, containment of noxious vapors and reduced crud formation. In addition to the description of operation, the paper presents the findings of laboratory tests of pulsed columns extracting copper from pregnant leach solutions and also delineates potential advantages of the pulsed column in copper solvent extraction.

Jan 1, 1999

By Renato G. Bautista

The prospect for recovery of rare earths from red mud, the bauxite tailings from the production of alumina is examined. The Jamaican red mud by far has the higher trace concentrations of lanthanum, cerium, neodymium, and yttrium. Scandium is also present. The dissolution of the rare earths is a major extraction problem because of the large volume of other materials present. The recovery processes that have been proposed include the production of co-products such as iron, alumina, and titania concentrates, with the rare earths going with the titania A critical examination of the possible chemical processes for the complete utilization of the red mud are presented Recommendations for research projects considered to be important in the development of a chemical separation process where no pig iron product is contemplated are also discussed.

Jan 1, 1992

By R. Togashi, S. Kuramochi, T. Yamada

In 1972, the Akita Zinc Co., Ltd. commenced operations with an annual capacity of 86,000 tonnes of electrolytic zinc, and it has operated with an annual capacity of 156,000 t-Zn since 1974. The business surroundings for non-ferrous metals production have become more severe with the high Yen rate for the dollar and low domestic demand in the last few years. Consequently, the company tried to survive with some improvements and succeeded to reduce operating costs and to improve profitability as follows: 1) expansion of its production capacity to. 196,000 t-Zn annually, 2) saving man-power by the introduction of fully-automated machines for cathode handling in the cellhouse, 3) improvement of the hematite process by means of the recovery of rare-metals. These improvements made Akita Zinc a competitive refinery in the modern world. We have been trying to improve the operations more and more. One of the challenges is to purify the iron oxide made in the hematite process by applying an As removal process, which is coming into operation in the near future.

Jan 1, 2000

By Jian Li, S. Penttilä, P. Liu, W. Zheng, C. Bibby

"The materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. The current Canadian pressure-tube supercritical water (SCW) concept design requires core outlet temperature of 650 °C at 25 MPa with peak cladding temperature reaching as high as 850 °C. Aside from oilier challenges, there is currently very limited data on candidate stainless steels' corrosion resistance under this operating condition. Austenite stainless steels that include 316L, 304H, AL6XN and 3 l0S that cover a wide range of Cr contents are promising candidates for either direct in core applications or as base coating materials. However, their corrosion resistance has not been tested systematically under this stringent condition. In this study, these types of stainless steels are tested, and their corrosion resistances are compared.IntroductionThe Canadian pressure-tube supercritical water (SCW) concept will operate at a core outlet temperature of 650 °C at a pressure of 25 MPa, with potential peak cladding temperature reaching as high as 850 °C. High-temperature corrosion resistance is one of the key design requirements for fuel cladding components. As summarized by Allen [1 ], most testing to date has been carried out at temperatures below 730 °C. To date, SCW corrosion data above 600 °C is very limited. Even at relatively low temperature exposure to SCW (e.g. 500 °C), F/M steels develop a thick oxide layer rapidly, while some austenitic stainless steels develop thinner surface oxide. Ni based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of intermetallic precipitates [2-5]. Dissolution of major alloying components from all of these alloys could also pose significant problems for downstream piping [6]. Kaneda et al. [7] suggested some modified stainless steels provide better SCW general corrosion resistance, with no sign of SCC under the slow-strain rate test.Cho [8] suggested that as the Cr content increase, general corrosion resistance improved at 510 °C and 25 MPa. However, similar to Cho's work, most of the SCW corrosion resistance assessments were based on weight change measurement. This can be unreliable due to potential exfoliation of thick oxide film. Besides, there have been no systematic SCW corrosion resistance tests for candidate stainless steels under higher temperatures. SCW corrosion rate increase dramatically for alloys tested at 600 °C [1]. It is also important to understand the role of major alloying elements under this stringent operating condition, not only for fuel cladding components' materials selection, but also for coating materials development."

Jan 1, 2013

By José Sancho, Julia Ayala, Purificación García, Begoña Fernández

"Electrofilter dust, a residue generated in the last stage of the Bayer process in the hydroxide aluminum calcination, was characterized to evaluate the alumina that was potentially extractable with sulfuric acid. The process studied aims to produce aluminum sulfate for water coagulant uses, taking advantage of the residues that accumulate in large quantities in the proximity of plants with difficult recycling for storage. Acid leaching is carried out at different concentrations of sulfuric acid, at different temperatures, pulp densities, and times, to dissolve gibbsite and transition aluminas. The result is an aluminum sulfate solution without iron and with commercial specifications.IntroductionElectrofilter dust is a residue generated in the last stage of the Bayer Process [1] in the hydroxide aluminium calcination. The residue is a mixture of alumina and hydrates which have not completed their calcination process.Electrofilter dust, composed by alpha alumina, gibbsite and transition aluminas [2] can be leached in an acid medium by putting most of the aluminium in solution; the remaining residue should be mainly andisolved alpha alumina. In many hydrometallurgical processes, sulphuric acid has been selected as the cheapest and the most effective leachant [3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]The aim of this study is to determine the effect of temperature, acid concentration and pulp density on the sulphuric acid leaching of electrofilter fines for aluminium dissolution, in order to produce aluminium sulphate for water coagulant uses. This will provide a commercial product and at the same time eliminate the environmental problem created as a result of the storage of large quantities of electrofilter fines in the vicinity of the Bayer plant."

Jan 1, 2008

By V. G. Papangelakis

The implementation of a flow-through yttria-stabilized zirconia (YSZ) sensor for pH measurements in high temperature and concentrated electrolyte systems relevant to hydrometallurgical processing of nickeliferous laterites is discussed. Instrumentation involved the use of a custom made flow-through titanium electrochemical cell. Accuracy and validity of the pH measurements at temperatures up to 250C were assessed using concentrated sulphate process solutions ranging from synthetic binary sulphuric acid ? water solutions to progressively multicomponent metal ? sulphate solutions simulating laterite Pressure Acid Leach conditions. The measurements were also compared with theoretical models using recently obtained thermodynamic data. A difference of ±0.25 pH units was observed between measured and calculated pH values at temperatures. This is an acceptable difference given that these are the first direct high temperature pH measurements ever on the concentrated acidic sulphate solutions. This result is encouraging more research for the development of industrial electrochemical systems for direct pH measurements in autoclaves.

Jan 1, 2003

By R. Chiarizia

Third phase formation, i.e., the splitting of the organic phase in two layers, is a common feature observed, under conditions of high loading, for many solvent extraction systems of both analytical and industrial interest. Although this phenomenon has been investigated in a large number of works, a structural and physico-chemical description is still lacking. In this work, small-angle neutron scattering (SANS) data for the tri-n-butylphosphate (TBP)-n-octane,Th(NO3)4-HNO3 solvent extraction system have been interpreted using the Baxter model for hard-spheres with surface adhesion. The increase in scattering intensity in the low Q range, observed when increasing amounts of HNO3 and/or Th(NO3)4 are introduced into the organic phase, has been interpreted as arising from interactions between small reverse micelles containing three TBP molecules plus solutes in their polar core. This intermicellar attraction, under appropriate conditions, leads to third phase formation.

Jan 1, 2003

By Yeliz Demiraya, Onuralp Yucelb

"Production of strontium metal from its oxide was studied under the pressure of 1-5 mbar by methalothermic process. SrO with 99 % purity was used in the experiments. Effects of Al powder addition (100, 200, 300 % of stoichiometric ratio) and time were investigated on recovering of metallic strontium. Effects of BaO addition (100 %, 200 %, 300 %) was also investigated. The final residues were examined for their chemical composition. XRD, AAS and Flame Photometer were used for chemical analysis. More than 96 % of strontium metal recovery can be obtained.IntroductionStrontium is an element which is used in many advanced technology applications. Barium strontium titanat, strontium bismuth titanat, and strontium bismuth tantalat thin films are promising materials in ferroelectric and Schottky-based microelectronics technologies, especially for memory applications. Physical vapor deposition (PVD) techniques as magnetron sputtering, thermal evaporation and molecular beam epitaxy (MBE) are the most widely used methods for growth of these thin films [1-3]. In these techniques high-purity of Sr metal is used as evaporation sources and sputtering targets. Furthermore, metallic strontium is used as a ""getter"" in electron tubes, and as an alloying elements in aluminum alloys [4].The most used Sr compound is SrCO3 and widespread process used in production of SrCO3 is the hydrometallurgical carbonation of celestite. Although there are considerable amount of Selestite reserves, SrCO3 and strontinum metal are not being produced in Turkey, yet [5].Concentrated celestite (SrSO4) is conversed to SrCO3 in carbonate media. Black ash and direct conversion processes are currently used methods. There are many satisfactory studies about hydrometallurgical carbonation of celestite and decomposition of SrCO3 [6, 7]. Since strontium metal is produced from it’s oxide (SrO), SrCO3 needs to be decomposed to SrO."

Jan 1, 2011

By Jorge Alberto Soares Tenório

Electronic components have precious metals like Au and Ag. These metals have a high performance in electric conductance. The recycling of the scrap, however is too difficult because of the presence of other metals like Fe, Al, Zn, Sn, ceramics and plastics, all together in electronic components. The aim of the present work was to define one way for physical separation to have metallic non-ferrous concentrates. It was used three kinds of scrap. I was used conventional equipment for mineral processing like hammer mill; screens, electrostatic and magnetic separation.

Jan 1, 1997

By Anjali Talekar

Low temperature heat capacities of pentaerythritol [PE: C(CH2OH)4], pentaglycerine [PG: (CH3)C(CH2OH)3], and 2-amino-2-methyl-1,3-propanediol [AMPL: (NH2)(CH3)C(CH2OH)2]have been determined by adiabatic calorimetry from 3 K to 300 K. To the best of our knowledge, this is the first reported heat capacity measurement below 280 K for PE and AMPL. The Debye temperatures for these organic crystals have also been determined and compared with other alcohol derivatives of neopentane.

Jan 1, 2006

By Jean Igor Margem, Lucas Barbosa de Souza Martins, Frederico Muylaert Margem, Noan Tonini SImonassi, Sérgio Neves Monteiro, Rômulo Leite Loiola

"Fibers of giant bamboo (Dendrocalmus Giganteus) are amongst the strongest lignocellulosic fibers. Although studies have been already performed, limited information exists on the mechanical properties of polymeric composites reinforced with continuous and aligned giant bamboo fibers. This work evaluates the tensile strength of this type of composite. Standard tensile specimens were fabricated with up to 30% of fibers aligned along the specimen's length. The fibers were press molded with a commercial epoxy resin mixed with a hardener and cured for 24 hours at room temperature. The specimens were tested in an Instron machine and the fracture surface analyzed by scanning electron microscopy. The tensile strength increased significantly with the amount of giant bamboo fiber reinforcing the composite. This performance can be associated with the difficult of rupture imposed by the fibers as well as with the type of cracks resulting from the bamboo fiber/epoxy matrix interaction, which prevents rupture to occur.IntroductionDue to growing concern about the ambient impacts from industrial activities, our society is ever more using environmentally friendly materials. In this regard, cellulose-based natural fibers, known as lignocellulosic fibers, become a promising solution. Nowadays, they are being considered as a substitute for synthetic fibers, such as glass fiber, used by the industry on a large scale [1-5]. The application of these natural fibers is also motivated by many advantages like good toughness and less wear of equipment used in the processing of composites. In addition, such composites are environmentally friendly because they are renewable, biodegradable and neutral with respect to C02 emissions, the main responsible for global warming and climate changes. [3,5,6].Lignocellulosic fibers also have some disadvantages in relation to synthetic fibers such as the difficulty of coupling with polymer matrices, due to the hydrophilic character of fiber and the hydrophobic nature of the matrix, as well as dimensional heterogeneity [ 4,5]. This last one is characteristic of the nature of this material and constitutes an obstacle to the use of these fibers in certain projects, especially those that aim high performance. The above mentioned disadvantages are worrisome reasons for the occurrence of reduction in the strengthening capacity, as indicated by the rule of mixtures for composites [7]."

Jan 1, 2013

By Alhondra de los Santos, Jesús L. Valenzuela, Jose R. Parga

"The present study evaluated the feasibility of using iron species generated by electrocoagulation (EC) as an adsorbent for removal As(III/As(V) from aqueous media. The full potential of EC was evident in that more than 99 percent of arsenic was removed without addition of chemical reagents. The adsorbent iron-species generated by EC was characterized by Chemical Analyses, X-Ray Diffraction and Scanning Electron Microscopy. The experimental data were correlated by employing a Langmuir adsorption isotherm. Thermodynamic parameters such as ?H o , ?S o and ?Go were calculated. The adsorption process was found to be exothermic and spontaneous.1. IntroductionArsenic contamination in potable water supplies is a serious health problem in many countries around the world. Groundwater arsenic contamination in La Comarca Lagunera Mexico was first reported 30 years ago [1]. Arsenic concentration has been found in well water from several communities ranging from 0.25 to 1.0 ppm. The elevated concentration of arsenic in water, above that originating from natural sources, has been attributed to the use of organoarsenical pesticides in the cotton fields and also to the millions of tons of waste slag generated at a local lead smelter [1]. The main arsenic species present in natural waters are arsenate ions 3- 4 AsO (oxidation state V) and arsenic ions H3AsO3, - 2 3 H AsO and 2- 3 HAsO oxidation state III). However, As(V) ions are most prevalent in oxygenated water while As(III) is found for anaerobic conditions, such as in well water or in groundwater. Conventional methods of arsenic removal rely on chemical-based treatment with lime, alum coagulation, iron coagulation and chemical oxidation. Other processes used with varying degrees of success include adsorption onto activated carbon, reverse osmosis, nanofiltration, manganese dioxide, magnetite and ionexchange resins [1-3]. These conventional processes generate a considerable quantity of secondary hazardous waste such as solid sludge, which also pose serious environmental problems. These drawbacks have forced various industries to search for effective, alternative treatment technologies for arsenic with a preference for electrochemical methods."

Jan 1, 2008

By Wilson Acchar, Fernando Barcelos, Luis Carlos Pereira

"Porous ceramics have been extensively investigated as structural materials for flow of fluids in many applications, such as filters for molten metals, water purification and hot gases, thermal protection systems and heat exchangers. This class of material must have two special features: high permeability and mechanical strength. However, these parameters are influenced in different ways by the processing method and the consequent cellular structure. In this work two different types of commercial ceramic filter materials are investigated. Characterization included the evaluation of the strength values as well as the permeability behavior and microstructural analyzes of the surface fracture. The results indicate that the strength values are strong dependent on the filament defects.IntroductionCeramic materials with a cellular structure have been extensively investigated as structural materials for flow of fluids applications [1-3]. Microstructural aspects such as morphology, size of the cell and the degree of interconnectedness are mainly parameters that influence the properties of these porous materials [4-6]. The most used industrial process to produce cellular ceramics for filter application is the polymeric sponge replication method. This technique consists in dipping the polymer foam into slurry containing an appropriate binder and the necessary ceramic materials, followed by a heating treatment [2,5].Mechanical properties of cellular ceramics depend basically on cell size, degree of interconnectedness and density [1,2,5,8,9]. Materials used as filters required a good strength and also permeability values. These properties are inversely proportional to each other. Higher porosity increases permeability values but decreases the strength values [1,2,5]. The objective of this work is to study the strength resistance of a commercial porous ceramic material (10, 20 and 30 ppi) based on silicon carbide."

Jan 1, 2012

By W. C. Chang

Phases and magnetic evolutions of melt spun Nd9.5(Fe1-xCox)85.5B5 (x=0, 0.05, 0.1 and 0.15), (Nd1-yLay)9.5Fe85.5B5 (y=0, 0.0.5, 0.1; and 0.15) and (Nd0.95La0.05)9.5(Fe1-zCrz)81.5B9 (z=0, 0.033, 0.067 and 0.1) nanocomposites: have been investigated. It was found that a. dilute Co substitution for Fe, x=0:05-0:15, in Nd9.5(Fe1-xCox) 85.5B5 improved not only Curie temperature but also the remanence and maximum energy product. Partial substitution of La for Nd in(Nd1-yLay)9.5Fe85.5B5 may suppress the grain growth of the materials during thermal treatment. Exchange coupling between the Nd2Fe14B and a-Fe was found: to increase with increasing La content. A dilute La-substitution, y=O. 10, has proven to decrease the optimum wheel speed required for preparing melt spun ribbons with better magnetic properties; Furthermore; a slight substitution of La for Nd in (Nd0.95La0.05)9.5(Fe1-xCrx)81.5B9 nanocomposite reduced the crystallization temperature of the over-quenched ribbons and led to the formation of a multiple phases mixture. Nevertheless, a dilute Cr addition increases the Tg of (Nd0.95La0.05)9.5(Fe1zCrz)81.5B9 and also suppresses the formation of the undesired (Nd,La)2Fe23B3 and Fe3B phases: Cr was found to play an important role in grain smoothening or magnetic separation which consequently increased the Hc of Cr-containing materials.

Jan 1, 1997

By C. Wieckert

Concentrated solar energy can be used as heat source for the production of metals. One of the most promising respective processes, the solar carbothermic production of Zn from ZnO, is investigated within the European research project SOLZINC, a cooperation of institutes and industries from France, Germany, Israel, Sweden and Switzerland. The solar produced Zn can be used as commodity or as an energy carrier for further processing on demand to electricity in Zn-air fuel cells/batteries or to generate hydrogen by reaction with steam. In both cases the Zn is oxidized to form ZnO, which can be recycled back to the solar plant. In these cyclic processes Zn acts as a means to store and eventually transport solar energy. Second product of the solar process step is a CO-rich offgas, which may e.g. drive a gas engine or may be shifted to hydrogen in a conventional reaction with steam. A pilot plant using 300kW concentrated solar power input has been constructed and operated successfully. 86mass-% of ZnO mixed with 14mass-% of charcoal are reacted to produce Zn and CO at a temperature of about 1200°C, yielding about 50 kg gaseous Zn per hour. Zn-dust with 95% purity is recovered from the offgas system that was designed to produce Zn for Zn-air fuel cells. Based on the results and findings from the pilot plant, a two tons Zn/h solar demonstration plant has been designed conceptually. Cost studies have been performed and scenarios for producing electricity or H2 via these ZnO/Zn-cyclic processes are evaluated.

Jan 1, 2006